import java.util.Random;

public class 随机验证码 {
    public static void main(String[] args) {
        String str = getCode();
        System.out.println(str);
    }
    public static String getCode() {
        char[] cha = new char[52];
        for(int i=0;i<cha.length;i++){
            if(i<=25){
                cha[i] = (char)(97+i);
            }
            else{
                cha[i] = (char)(65+i-26);
            }
        }
        Random r = new Random();
        String str = "";
        for(int i=0;i<4;i++){
            int a = r.nextInt(52);
            str += cha[a];
        }
        int i = r.nextInt(10);
        str += i;
        return str;
    }
}
